2 Inheritance Parents and offspring often share observable traits. Grandparents and grandchildren may share traits not seen in parents.Why do traits disappear in one generation and reappear in another?
3 A pedigree is a chart that shows how a trait and the genes that control it are inherited within a family.
5 Genetic predictions Ellen and Michael’s parents must be carriers. Ellen’s brother Michael hassickle cell anemia, an autosomal recessive disease.A aAaAAAaaaEllen is not affected andcannot carry aa genotypeWhat is the chance that Ellen’s child has a sickle cell anemia allele (a)?EllenMichael?Chance Ellen is a carrier = 2/3Chance child inherits sickle cell allele = 1/2Overall chance child carries sickle cell allele from Ellen = 2/3 x 1/2 = 1/3
6 Autosomal recessive inheritance Heterozygous individuals carry the recessive allele but exhibit the dominant phenotype.Males and females are equally affected and may transmit the trait.May skip generations.
8 Sex chromosomes determine gender Human males are the have two different sex chromosomes, (XY).Human females only have one (XX).
9 What determines gender? Number of X chromosomes, or presence of Y chromosome?X0Female with Turner syndromeXXYMale with Klinefelter syndrome
10 X-linked traits Males One X chromosome Inherited from mother Two possible genotypesXNYXnYHave trait or do not have trait- they can’t be a carrier!FemalesTwo X chromosomesInherited from both parentsThree possible genotypesXNXNXNXnXnXnHeterozygous individuals are carriers of recessive traits- they can pass it down to their offspring- especially their male children!
11 X-linked recessive traits Always expressed in males if the male inherits the recessive gene from the mother.Affected males: Inherited from motherFemales need to be homozygous recessive to show the traitAffected females : Fathers affected or mother had the trait or carried it!
12 X-linked dominant inheritance Expressed in females with one copy.Males are often more severely affected.Typically associated with miscarriage or lethality in males.
13 BLOOD TYPEHuman blood type genes are an example of a codominant trait- meaning a trait with more than one set of alleles.Phenotype : A B AB OGenotype : AO, AA BO, BB AB OO